I believe the consensus is that it's not worth the upgrade if you're on Sandy/Ivy Bridge, but can be worth it for older chips. The major disappointment is that Haswell's TIM doesn't dissipate heat very well, leading to a lower overclock ceiling (in terms of raw MHz) compared to its Sandy/Ivy Bridge predecessors. The minor IPC improvement and new AVX2 instructions do offset that, so it's ever so slightly better than Ivy.

On the plus side, note that Haswell's corresponding 8-Series motherboards (e.g. Z87) include new functionality as compared to older 6-Series and prior boards (e.g. native SATA-III, USB 3.0, and PCIe 3.0) which is nice to have..

In your case, I believe that a Haswell i5 will greatly improve your performance versus your current Core 2 Duo. Then again, you could also go with a discounted Ivy Bridge + Z77 motherboard setup if you find one discounted and it would work just about as well.

Hmm im in a dilemma .. Im between 2 Scenarios. Next year im going to university so i will need a Good,fast pc + gaming

1) Upgrade my Core 2 Duo to a 2600k For example so i can pass this final year in school. I will also change mobo,ram ofcourse. i found the parts from a store and the total is 380euro. And buy a new pc next year.

2) Build a haswell machine right now, new cpu,mobo,ram and with my current GPU,case,psu and HDD + SSD
and next year buy new parts like (Gtx 780 or AMD 8000series depends, new HDD,SSD,CASE,Monitor etc...) .

What do you think? Should i make a minor upgrade to 2600k ? Or build a "half" haswell pc and the other "half" next year ?

Its a great CPU in my view (so far )
Of course if you already have the excellent Sandy Bridge or Ivy Bridge you are not going to see a massive different, just like you didn't see a massive different between Sandy - Ivy.

Then again Sandy Bridge is only 2 years old + a bit

What I do find funny is when people have a go at performance increases only being 10%, the thing about percentages is they are dependent on the value they are being drawn from.

To keep it simple lets put it like this
say Sandy Bridge gave you 1000 thingies
Ivy Bridge came in at 10% more so you got 1100 thingies

Haswell comes along with another 10% which gives you 1210 thingies

the physical increase is bigger

Of course we are just running numbers there and not dealing with the experience, how it feels to use, how it handles the applications that we run, which ends up being more of a personal thing. I have always felt that no matter which Intel cpu you get , they are just "peppier" than AMD Cpu's

I bought AMD last time as I was on a budget, and the bang for buck was insane, but I have saved up to get that extra "pep".

The new motherboard chipsets are amazing, the software that came with my Gryphon is outstanding, fan profiles making the machine quieter than ever, absolutely loving it, and at the end of the day, this is a hobby for me and I love tinkering inside my machine as much as playing games, so no doubt it will evolve with me where time and wallet contents permit

What do you think? Should i make a minor upgrade to 2600k ? Or build a "half" haswell pc and the other "half" next year ?

Thanks in advance

Most of your current hardware (with the exception of the CPU/motherboard/RAM) is serviceable enough. What I'd recommend getting is a Haswell i5-4670K, a matching Z87-chipset motherboard (perhaps a Gigabyte GA-Z87X-D3H or -UD3H) and a 2x4GB kit of DDR3-1866 or DDR3-2133 RAM to start with.

The above configuration should last for several years, and you would still be able to reuse your current GPU, SSD and HDD without problems. Of course I'd recommend replacing your Radeon 6870 with a higher-performance current or next-gen card next as funds allow, but that should be a secondary priority.

IMO Haswell is not flash for Overclockers but they are good for everyone else. Decent improvement over SB but not compelling.

If I was on SB or looking for big Overlocks then Id would give it a miss. Anything else its a very worthwhile upgrade. Great choice in Mobos as well and some nice features in z87. Now that I OC less these days Im considering switching back to Intel. I like the bigger focus on gaming specific mobos.